Larus cachinnans in the Netherlands

(last update: August 16, 2020)

Coordinators:
Albert de Jong
Leon Kelder
Roland-Jan Buijs
Thijs Horst
Merijn Loeve
Mars Muusse

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Caspian Gull cachinnans U|6 adult, 2026, the Netherlands. Picture: Thijs Horst & Mars Muusse.

You can participate in this project too! Please send in your observations of colour ringed birds to: ring@buijsecoconsult.nl

Tibia ring G-U|6 and metal NLA 6.260.166, ringed as breeding 8CY male Larus cachinnans on April 26 2026 in nest XCHP at Lelystad, the Netherlands. Ringed by Thijs Horst (Roland-Jan Buijs ringing team).

Visits and data 2022.

11-04-2022 XCHP present, low on blocks.
12-04-2022 XCHP & partner present.
15-04-2022 XCHP & partner present.
      length width water test  
29-04-2022 2 eggs A egg 68,1 49,9 float - 2 mm XCHP & sub-adult partner. 2 eggs clutch.
B egg 68,6 51,1 float - 1 mm XCHP is hybrid type (no mirror P9) en 4CY is subad cach type.
09-05-2022 XCHP present. No chicks found.
17-05-2022 metal: darvic: mass: Head + Bill Bill
pullus .5625128 r-51 285 74,4 --
pullus .5625129 r-50 351 77,4 --
22-05-2022 No chicks found.
30-05-2022 metal: darvic: mass: Head + Bill Bill
pullus .5625128 r-51 764 99,5 36,6
pullus .5625129 r-50 861 104,7 41
02-06-2022 y-XCHP & partner present.
21-06-2022 y-XCHP & partner present.
  r50 & r51 swimming and flying south of dam 2.
28-06-2022 y-XCHP & partner present.
  r50 & r51 swimming and flying south of dam 2.
17-07-2022 photographed y-XCHP
 
Visits and data 2023.
 
egg sizes & volume 2023
SPECIES NEST A_length A_width A_volume B_length B_width B_volume C_length C_width C_volume TOTAL NEST: known parents?
cach x cach XCHP 70,6 52,2 96,86 67 52,7 93,69 68,3 50,8 88,75 279,30 same as 2022
ring pulli: 12-mei laying A egg: 7-apr hatch A egg: 5-mei
     
catch: date: metal: darvic: mass: wing: head+bill:      
Pullus 11-05-2023 5.556.464 r-8S -- -- --
Pullus 11-05-2023 5.556.465 r-89 -- -- --
Pullus 18-05-2023 5.556.465 r-89 550 -- 80,4
Pullus 27-05-2023 5.556.464 r-8S dead > 7 days ago.
Pullus 18-06-2023 r-89 1103 362 130,7
 
XCHP
dam: dam 2 east
location: below large boulders, east side of blocks, closer to bitumen than 2022.
breeders: cach x cach
OBSERVATIONS:
04-04-2023 adult: yXCHP present with partner.
05-04-2023 adult: yXCHP present with partner.
09-04-2023 adult: 2 adult cach present. One is yXCHP.
nest: 2 eggs measured. No watertest, ring chicks in 1st session.
26-04-2023 nest: 3 eggs, all measured. Red spot sprayed on stone.
27-04-2023 nest: 3 eggs.
adult: yXCHP present with partner.
11-05-2023 pulli: 2 chicks ringed, 1 egg rotten
13-05-2023 adult: yXCHP pictures.
18-05-2023 pulli: R-89 present
27-05-2023 pulli: dead chick near nest r-8S, dead >7 days.
18-06-2023 pulli: r-89 present. Fledging success: 1 chick.
25-06-2023 pulli: r-89 present with both parents

Visits and data 2024.

NEST code parent 1 parent  2 A_length A_width A_volume B_length B_width B_volume C_length C_width C_volume TOTAL NEST:
XCHP 2024 cach cach 70 52,6 97,51 69 52,8 96,85 68 51,6 91,16 285,53
  # eggs A-egg hatch # ringed chicks # all chicks # fledged chicks comments
  3 10-4-2024 8-5-2024
   
dam: dam 2 east
location: below large boulders, east side of blocks, closer to bitumen than 2022.
parents? same as 2022, 2023
   
ring pulli: 12-May
date darvic metal location / nest# species sexe age wing mass head+ bill bill tarsus gonys greyscale
14-05-2024 g-B|S .5631170 nest XCHP PONT 1CY 200          
14-05-2024 g-B|T .5631171 nest XCHP PONT 1CY 273          
                           
OBSERVATIONS:
12-04-2024 eggs: 2, measured.
adults: yXCHP & partner present
21-04-2024 eggs: 3 eggs, measured.
23-04-2024 adults: yXCHP & partner present
02-05-2024 eggs: 3 eggs.
14-05-2024 chicks: 2x ringed and measured.
food: Round Goby (zwartbekgrondel / Neogobius melanostomus) and worms.
04-06-2024 adult: y-XCHP & partner present and aggressive.
18-06-2024 chick: CONTROLL: g-B|T at water.

Visits & data for 2025:

2025 parent 1 parent 2 A_length A_width A_volume B_length B_width B_volume C_length C_width C_volume
TOTAL NEST:
 # eggs
y-XCHP (055) XCHP hybrid cach 69,4 52 68,1 51,2 68 52,6 3
dam:
dam 2 east
location:
was nest 55-2024, Between 2 large boulders, top of dam 2, Orange jerrycan,
parents:
same as 2024. XCHP is hybrid type Caspian Gull.
OBSERVATIONS:
16-03-2025 nest
XCHP present on block dam 2, near 2024 location, with several cach (likely incl partner),
20-03 nest
XCHP present near nest
21-04 eggs
3x eggs measured,
28-04 nest
XCHP present
08-05 adult
both partners present
25-05 nest
2 eggs, no chick found,
09-06 nest
2 eggs, 2nd clutch??
14-06 nest 2 eggs
25-06 nest
1 egg, warm
29-06 nest
1 egg warm. Season failed for XCHP.

Visits and data nest y-XCHP & g-U|6 (2026).

2026 parent 1 parent 2 A_length A_width A_volume B_length B_width B_volume C_length C_width C_volume
TOTAL NEST:
 # eggs
XCHP & g-U|6 cach cach 66,9 52,9         1
 
ringed:
date darvic metal location / nest# species sexe age wing mass head+ bill bill tarsus gonys barcode
26-04-2026 G-U|6 6.260.166 XCHP PONT M 8CY 469 1073 139,1 63,9 75,9 20,5 26B02652
10-05-2026 Y-0:R 5.646.706 XCHP & U|6

PONT

 pullus 56  
               
OBSERVATIONS:
22-04-2026 nest 1 egg, measured. With one Goose Egg.
26-04-2026 nest 1 egg + 1 goose egg.
  parent Adult trapped at nest. Now G-U|6.
  food Roach.
10-05-2026 pullus 1x ringed, is only chick from nest 1 egg.
    Goose egg hatched as well. Where is the chick?
     

below: Caspian Gull cachinnans U|6 adult, April 26 2026, colony Lelystad, the Netherlands. Picture: Thijs Horst & Mars Muusse.